The traditional flanges are mostly processed by die-casting, so they are of integral structures. Even for a weld neck flange, it is also formed by processing two flange assemblies by die-casting and then integrally fixing the two flange assemblies by welding, and such weld neck flange is common in pipe welding.
After a flange is processed, the thickness of the flange is non-adjustable, and each kind of flange has a respective installation thickness. When the connection thickness of the flange is changed, it is needed to replace the flange with a suitable flange, and a flange with a suitable installation thickness is to be adopted and then installed. Therefore, even if the installation diameter is equal, the flange structures may also vary in thickness specifications. If the thickness of the flange is appropriate, several thin flanges may be installed by overlapping, but this installation manner is not always convenient.
The existing connection of flanges is achieved by bolts, therefore, connection pieces are generally provided with connection holes for bolts. Or, flanges are fixed to the end parts of the connection pieces, the connection of the connection pieces becomes connection of two flanges, and then the two flanges are connected by bolts. If the end parts of the connection pieces are unsuitable to process connection holes for bolts or unsuitable to fix flanges due to their shape structures, the traditional flanges can not be used. Therefore, a flange suitable for this case is in urgent need.
The existing flanges are generally circular, with connection holes processed on the flanges for bolts to pass through. So the structure is relatively simple, and such flanges can be processed by die-casting. However, as some connection pieces have relatively complex structure, the connected flange structures appear different from the traditional flange structures. It becomes very difficult to process flanges by the traditional die-casting way at this time.
The Patent Office of China published a patent No. CN2566088Y on Aug. 13, 2003, titled FLANGE FOR RUBBER JOINT. This flange comprises a flange main body, wherein the flange main body is formed by combining multiple sector plates through a connection mechanism. The structure of the flange main body formed by combing multiple sector plates is still a circular structure, and the installation of the flange is still achieved by bolt connection, so this flange is not suitable for connection pieces with non-bolt connection.
The Patent Office of China published a patent No. CN2694084Y on Apr. 20, 2005, titled COMBINED STEEL-PLASTIC COMPOSITE FLANGE. This flange is formed by splicing and then bonding two symmetrical steel-plastic composite semicircular rings with metal gasket therein. The steel-plastic composite semicircular rings are provided with connection holes for bolts to pass through. The two ends of the steel-plastic composite semicircular rings are provided with step-shaped bonding surfaces for the two steel-plastic composite semicircular rings to splice. The composite members are formed by die-casting and then still connected by blots after spliced, so this flange is not suitable for connection pieces with non-bolt connection.